After five seasons, Stranger Things 5 Vol. 2 finally gives us the answer we’ve been waiting for. Dustin gets a hold of Dr. Martin Brenner’s journals, which explains what The Upside Down actually is. It’s not a parallel universe or a cursed mirror image of Hawkins, Indiana.
It’s a wormhole. A tunnel or “bridge” linking Hawkins to an evil, older world called the Abyss, also known as Dimension X.
And that tunnel was accidentally created by Eleven the night she first met the Demogorgon.
How Eleven Created the Bridge
Back on November 6, 1983, Dr. Brenner ordered Eleven to use her psychic powers to search for Henry Creel (001/Vecna). Her search led Eleven to the Demogorgon residing in the Abyss. When she made contact with the Demogorgon, her powers ripped through space-time.
That tear carved out a tunnel that opens an unstable wormhole between Hawkins and the Abyss. The result was what we now call the Upside Down.
Why It Looks Like Hawkins
The Upside Down mirrors Hawkins because the tear originated inside Hawkins Lab. The wormhole anchored itself to that location, copying its surroundings as the basis for its form. The vines, spores, and growths are from the Abyss’ alien environment seeping through it.
It explains why the Russians couldn’t open their own gate in Kamchatka back in season 3. That’s because there isn’t a wormhole linking the peninsula to the Upside Down. Without that anchor, there’s no access point.
How the Wormhole Works
The Upside Down functions like a physical tunnel connecting two distant points. Anything that enters the tunnel on the Hawkins side can emerge on the Abyss side.
The Upside Down isn’t infinite. Outside its walls lies nothing but an empty void.
Gates in Hawkins are sort of like portals that connect the town’s physical space to the interior of the wormhole. When someone enters a gate, they appear inside the Upside Down. Rifts along the tunnel’s ceiling lead out toward the Abyss, which is how Vecna and his monsters are able to enter Hawkins.
Exotic Matter is the Glue Holding It All Together
The Upside Down is extremely unstable. Under normal circumstances, the tunnel would collapse under its own pressure. The only reason it holds is because of exotic matter, the strange energy source Brenner discovered beneath Hawkins Lab.
In real theoretical physics, exotic matter represents material with negative energy or repulsive gravitational effects.
In Stranger Things, Brenner harnessed that concept to preserve the link to the Abyss. His lab used concentrated exotic matter to reinforce the wormhole after Eleven tore it open. The energy pushes outward on the tunnel “walls” to keep it from snapping shut.
In Volume 2, we see why this is important. When Nancy shoots at the exotic-matter core inside the Upside Down version of the lab, the tunnel fractures. The vine-covered walls tear open to reveal pure nothingness, exposing a vacuum outside the Upside Down.
Why Destroying It Could Save Hawkins
After reading through Dr. Brenner’s journals Dustin figures they need to destabilize the exotic matter that’s keeping the wormhole stable. If the tunnel collapses, it will sever the link between the Abyss and Hawkins for good.
Without the wormhole, the Upside Down will cease to exist, destroying everything inside of it. Vecna seems to be aware of that fact, which is why he’s trying to merge the Abyss with Hawkins before anyone can close the bridge.
With the series finale dropping on December 31 8:00 p.m. EST, the stakes couldn’t be higher. Can The Party destroy the exotic matter before Vecna succeeds with his plan? Or is Hawkins too intertwined with the Abyss to survive the destruction of the Upside Down?
Whatever happens, the Upside Down is no longer a monster’s lair or a parallel Earth. It’s a man-made bridge, built by accident, sustained by science, and haunted by consequence. And like every wound in Stranger Things, the real danger was never just what came through the gate. It was that we opened it at all.
